Control apparatus



March 6, 1962 F. T. DEZIEL CONTROL APPARATUS Filed Jan. 12, 1959 INVENTOR. FRED T DEZIEL A TTORNEY United States Patent 3,023,803 CONTROL APPARATUS I Fred T. Deziel, Bloomington, Minn., as'si'gnor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Filed Jan. 12, 1959, Ser. No. 786,303 7 Claims. (Cl. 158-124) The present invention is concerned with an improved control apparatus and more particularly with an improved burner control apparatus utilizing a novel safe-start feature.

As is well known, electronic flame detectors have come into wide acceptance as the flame detector portions of combustion safeguard equipment which is used to monitor the proper operation of an associated fuel burner unit. These electronic flame "detectors utilize electronic devices which may possibly fail in a condition where a flame is falsely indicated. As a result, a so-called safe-start feature or checking feature has been incorporated into such electronic flame detectors. In broad principle, these flame detectors operate such that upon the initial application of operating voltage thereto, conditions are such that the flame relay is energized in response to a simulated presence of flame. Upon the flame relay being so energized, a further means "is energized which discontinues the simulated presence of flame and causes the flame relay to be de-energized. Circuits are now completed such that an associated fuel burner unit may be energized in an attempt to establish flame at the burner unit. With such a construction, the ability of the electronic flame detector to first sense the simulated presence of flame and to then sense the actual absence -of flame ispositivelychecked before the fuel burner unit is energized.

The present invention is directed to such a control apparatus and provides an improved checking or safe-start system.

Specifically, the present invention provides a construction whereby the flame relay, upon initially being energized due to the simulated presence of flame, causes the energization of a further means in the form of a safe-start relay which is provided with but a single switch connected to maintain the safe-start relay energized once it is initially energized and further discontinue the simulated presence of flame.

The construction provided by the present invention also provides means whereby a main burner control relay is energized by a circuit which is controlled by a single normally open switch of the safe-start relay such that if, due to contact contamination or the like, the single normally open switch of the safe-start relay should fail to make electrical contact, the fuel burner unit is not energized.

The present invention will be apparent to those skilled in the art upon reference to the following specification, claims, and drawing, of which the single figure is a schematic showing the preferred embodiment of the present invention.

Referring specifically to the single figure, the apparatus disclosed therein can be divided into three'basic components. The first of these components is an electronic flame detector designated by the reference numeral 10 and having electron discharge devices '11 and 12. The electronic flame detector 10 is in essence a two-stage amplifier in which the discharge device 11 forms the first stage and the discharge device 12 forms the second stage. The input of the electron discharge device 11 is controlled by a condition sensing means in the form of a photocell 1B. The output of discharge device 11 consists of a load in the form of resistor 14 which is connected to control the input of discharge device 12. The output of discharge device 12 controls a flame relay '15 having a winding 16 and switches 17, 1'8, 19, and 20. With the apparatus 'as shown, flame relay 15 is de-energized and switches 17 and 19 are open while switches 18 and 20 are closed.

The second basic component of the apparatus is identified by the reference numeral 21 and this component is a control network Which is controlled by means responsive to the need for operation of a fuel burner unit in the form of a bi-metal operated thermostat 22. Thermostat 22 controls the energization of 'a main burner control relay 23 having a winding 24 and switches 25 and 26. Here again, relay 23 is shown in its tie-energized condition wherein switches 25 and 26 are open. The reference numeral 27 identifies a safety'lockout means in the form of a conventional bi-metal operated safety switch having a normally closed switch 28, a bi-metal 29, and a bi-metal heater 30. Also incorporated within the control network 21 is a safe-start relay 31 having a winding 32 and a normally opened switch 33. It will be noted that safe-start relay .31 is provided with but a single switch and, as will be apparent hereafter, this switch is connected to provide not only the safe-start feature for electronic flame detector '10 but also to supervise the energization of main burner control relay 23.

The third main portion of the apparatus disclosed is the fuel burner unit identified by the reference numeral 34.

This fuel burner unit 'is provided with a inain burner 35 having a valve 36, a pilot burner 37 having a valve 38, and ignition means in the form of an ignition transformer 39. As will be apparent, upon a call for operation of the fuel burner unit 34 by thermostat 22, the improved control apparatus first completes a checking cycle and thereafter pilot valve 38 and ignition transformer 39 are energized to establish flame at the pilot burner '37. This flame is detected by photocell 13, and in response thereto, ignition transformer 39 is de-energized and main valve 36 is energized such that fuel is admitted to the main burner 35 and is ignited by the pilot flame present at pilot burner 37.

Operating voltage is supplied from power line conducr tors '40 and 41 through a master switch 42, which is shown in the open position. Operating voltage for the electrical components of electronic flame detector '10 and control network 21 is derived from transformers 43 and 44. Transformer 43 is provided With a primary winding 45 which is directly connected to power line conductors and 41, when switch 4-2 is in a closed position. This transformer is also provided with a secondary winding which energizes the filament heaters of discharge devices 11 and 12. The secondary winding 47 of this transformer supplies operating voltage for the second electronic stage including discharge device 12. The secondary winding 48 ofnthlig transformer supplies operating voltage for photoce The primary winding 49 of transformer '44 is adapted to be connected to the power line conductors 40 and 41, initially by means of switch 17 of the flame relay 15 and to be maintained connected to the power line conductors by means of switch 33 of safe-start relay 31. The operation of this portion of the circuit will be described.

Transformer 44 is also provided with a secondary winding 50 which is connected to supply operating voltage for discharge device 11. This transformer is also provided with a secondary Winding 51 which includes a tap at 52 and which provides operating voltage for the control network 21.

Operation The apparatus as disclosed in the single figure is in its completely de-energized position when master switch 42 is open. It should be mentioned that while the apparatus disclosed shows the use of a thermostat 22, it may be desirable in some instances to provide a direct connection to replace thermostat 22 and provide a controller of one type or another to perform the function of master switch 42. In this case, master switch 42 would be closed upon a need for operation of the fuel burner unit. However, for the purposes of this explanation, it will be assumed that switch 42 is a line switch which is closed to 'place the apparatus in an operative condition under the command of thermostat 22.

Upon the closing of master switch 42, the primary winding 45 of transformer 43 is energized. As a result thereof, the secondary winding 46 is operative to energize the filament heaters of discharge devices 11 and 12. The secondary winding 47 applies an operating voltage to the anode 53 and the cathode 54 of discharge device 12 through a series circuit including the winding 16 of relay 15, which winding is shunted by a capacitor 55. Secondary winding 48 is effective to apply an energizing voltage to the photocell 13 through a circuit which can be traced from the upper terminal of the secondary winding through a capacitor 56, conductor 57, anode 58 and cathode 59 of photocell 13, conductors 60, 61 and 62 to the lower terminal of secondary winding 48.

It will be noted that at this stage in the operation of the improved control apparatus, discharge device 11 is inoperative due to the fact that an operating voltage is not applied thereto. Therefore, this discharge device remains nonconductive and in effect, insofar as discharge device 12 is concerned, a flame is simulated. In response thereto, discharge device 12 conducts to energize flame relay 15.

Furthermore, since a flame is not present at the fuel burner unit 34, photocell 13, which is a photo-emissive cell and acts as a unidirectional current conducting device, does not pass current through the above traced circuit including capacitor 56. Therefore, capacitor 56 is not charged at this stage of the operation of the improved control apparatus.

Energization of flame relay 16 causes its switches to move from their de-energized to their energized positions. The switches 19 and 20 perform no control function at this time since the main burner control relay 23 is deenergized. The opening of switch 18 insures that relay 23 may not be energized during this phase of operation of the control apparatus. The closing of switch 17 com-' pletes an initial energizing circuit for the source of operating voltage which energizes discharge device 11. This source of operating voltage is transformer 44 and the energizing circuit for its primary winding 49 can be traced from power line conductor 41 through primary winding 49, conductor 63, switch 17, and conductor 64 to power line conductor 40. As a result thereof, the secondary winding 51 of this transformer is immediately effective to energize the winding 32 of safe-start relay 31 to thereby cause switch 33 to move to its closed position. It will be noted that switch 33 shunts switch 17 of the flame relay and therefore the primary winding 49 is maintained connected to the power line conductors 40 and 41'and also the safe-start relay 31 is maintained energized independent of any further state of operation of the flame relay 15.

However, in order for the safe-start relay 31 to be initially energized it is necessary that flame relay 15 respond to the simulation of the presence of flame.

.The secondary winding 50 of transformer 44 is effective to apply operating voltage to the discharge device 11. The

lower terminal of this secondary winding is connected by means of conductors 61, 65, and 66 to the cathode 67 of discharge device .11 and the upper terminal of this secondary winding is connected by means of conductor 68 and resistor 14 to the anode 69 of this discharge device.

Since a flame is not present at the fuel burner unit 34 at this time, discharge device 11 is rendered conductive. The current flow circuit of this discharge device can be traced from theupper terminal of transformer 50 through conductor 68, resistor 14, anode 69, and cathode 67, and conductors 66, 65, and 61 to the lower terminal of sec ondary winding 50. It can be seen that the voltage de- 4 veloped across resi'stof 14 is such that the cathode 54 of discharge device 12 is rendered positive with respect to the control electrode 70 of this discharge device. Therefore, discharge device 12 is cut off and flame relay 16 is de-energized. In this manner, the flame relay responds to the actual absence of flame at the fuel burner unit 34;

It is well to note at this point the advantage of eflergiz' ing the circuit including photocell 13 from the first to the energized transformer 43. It will be remembered that in initially discussing the energizing circuit for photocell 13, it was pointed out that since a flame is not present at fuel burning unit 34, capacitor 56 is not charged. However, assume for the moment that some fault or unusual condition arises wherein this capacitor 56 becomes charged, for example, a high background light intensity from a source other than a flame may cause photocell 13 to conduct and charge this eapacitor. Under such a condition, photocell 13 is unable to sense the presence or absence of flame due to this high background illumination and capacitor 56 in its charged state is effective to maintain discharge device 11 nonconductive after transformer 44 is energized. Therefore, flame relay 15 is maintained continuously energized and, as will be apparent, unless flame relay 15 is de-energized in response to the energization of transformer 44, the main fuel burner unit 23 may not be energized. In this manner, if a condition such as a high background illumination should exist, the fuel burner unit 34 remains de-energized even though thermostat 22 may be calling for operation of this unit.

In its normal operation, however, flame relay 15 is de-energized in response to energization of transformer 44. Upon this relay being de-energized, the switches 17, 18, 19, and 20 again assume their de-energized position as shown in the single figure. The apparatus is now in a standby condition wherein the electronic flame detector has correctly sensed the simulated presence of flame and then the actual absence of flame.

Assume now that there is acallfor operation of the fuel burner unit 34 as evidenced by thermostat 22 closing its associated switch. The closing of thermostat 22 causes an initial energizing circuit to be established for the main fuel burner relay 23. This initial energizing circuit can be traced from the upper terminal of transformer 51 through conductor 70, heater 30, conductor 71, switch 1 8, conductor 72, winding 24, thermostat 22, conductor 73, safety-switch 28 and conductor 74 to the lower terminal of the secondary winding 51. From this above traced circuit it can be seen that in order for the relay winding 24 to be initially energized, it is necessary that the actuating heater 30 of safety-switch 27 have electrical continuity; in other words, this heater must be in an operative condition. Furthermore, the flame relay 15 must be in a de-energized condition indicating the absence of flame at the fuel burner unit to thereby close its switch 18.

Energization of control relay 24 causes its switches 25 and 26 to move to a closedcondition. A closing of switch 25 completes a holding circuit for winding 23 which can be traced from the tap 52 of transformer 51 through conductor 75, switch 25, winding 23,thermo'stat 22, conductor 73, safety switch 28, and conductor 74 to the lower terminal of the secondary winding.

Closing of switch '26 completes an energizing circuit for the pilot valve 38 and the ignition transformer 39. This energizing circuit can be traced from power line conductor 41 through conductor 75, switch 26, conductor 76, pilot valve 38, and conductors 77 and 78 to power line conductor 40.

The energizing circuit for ignition transformer 39 extends from switch -26 through conductor 79, switch 20, conductor 80, ignition transformer 39, and conductors 77 and 78 to power line conductor 40. With the energization of the pilot valve 38 'and the ignition transformer 39, a pilot flame is established at the pilot burner 37.

This charge on capacitor 56 is distributed through an RC filter network including resistors 81 and S2 and capacitor 83 to charge capacitor 83 as indicated. This then biases the control electrode 84 of discharge device 11 negative with respect to the cathode 67 and discharge device 11 thereby comes nonconductive. The cut oil bias voltage normally developed across resistor 14 in the standby condition of the apparatus therefore no longer exists and discharge device 12 becomes conductive to energize the winding 16 of flame relay 15.

Switches 17, 13, 19, and 20 once again move from their de-energized to their energized positions. The opening of switch 18 opens the initial energizing circuit for the main burner control relay 23 which is now maintained energized through its own switch 25. Furthermore, the opening of switch 18 de-energizes the actuating heater 30 of safety switch 27.

In the event that a pilot flame had not been established, flame relay 15 would not have been energized and the heater 31 would be maintained energized to heat bimetal 29 such that its upper end warps to the right to cause the switch 28 to open, thereby d6l16I'giZlI1g the main burner control relay 23.

The opening of switch 2t de-energizes the ignition transformer 39 and the closing of switch 19 completes an energizing circuit for the main valve 36. This energizing circuit can be traced from power line conductor 41 through conductor 75, switch 26, conductor 19, switch 19, conductor 85, valve 36, and conductor 78 to the power line conductor 40. Fuel is now admitted to the main burner 35 and is ignited by the pilot flame at pilot burner 37.

The apparatus is now in the running condition wherein a flame has been established at the fuel burner unit 34 and this flame has been sensed by the electronic flame detector 19. Should this flame subsequently fail, the photocell 13 detects the absence of flame at the fuel burner unit 3 3 and discharge device 11 is once again rendered conductive to in turn render discharge device 12 nonconductive. The flame relay 15 thereby drops out and switch 18 closes to once again energize the actuating heater 30 of safety switch 27 whereas switch 19 opens to de-energize the main valve 36 and switch 26 closes toagain energize the ignition transformer 29 in an attempt to re-establish flame at the fuel burner unit 34. If a flame is not re-established, the safety switch 27 is eflective after a predetermined time interval, for example sixty seconds, to de-energize the main burner control relay 23 which then causes switch 26 to open de-energizing the entire fuel burner unit 34. It is now necessary to manually depress tLe reset button 86 to again place the apparatus in the standby condition.

From the above description it can be seen that I have provided an improved control apparatus wherein the single switch 33 of the safe-start relay 31 is effective to simulate the presence of flame and cause the second stage 12 of the electronic flame detector to be energized upon initial energization of the apparatus. In this manner, flame relay is energized.

The flame sensing means 13 is also energized at this time such that if a fault exists capacitor 56 is charged, as it should not be when a flame is absent at the fuel burner unit.

Furthermore, upon the flame relay correctly responding to the simulated presence of flame, switch 17 controlled by the flame relay energizes the second transformer 44 and causes the safe-start relay 31 to be energized. Switch 33 of this safe-start relay then shunts switch 17 of flame relay 15 and maintains transformer 44 thereafter continuously energized.

Safe-start relay 331 performs its safe start function with but a single switch and this switch is located in a high voltage circuit to thereby insure reliable switching. Energization of the transformer 44 removes the simulated presence of flame by rendering the first electronic stage 11 operative. Flame relay 15 is de-energized. However, the de-energization of flame relay 15 is dependent upon flame sensing means 13 properly sensing the absence of flame. Should a fault exist which causes capacitor 56 to be charged, then discharge device 11 is maintained in its nonconductive state so that flame relay 15 cannot be tie-energized, which in turn insures that main relay 23 cannot be energized.

Furthermore, not only are both electronic stage 11 and safe-start relay 31 energized from trans-former 44, but also the main burner control relay 23 is energized from this transformer. In this way, should the switch 33 of safe-start relay 31 fail during the standby of the apparatus, for example due to contact contamination, the circuit which is arranged to energize the main burner control relay is immediately opened and relay 23 cannot be energized by action of thermostat 22.

Other embodiments of this invention will be apparent to those skilled in the art and it is therefore intended that the scope of the present invention be limited solely by the scope of the appended claims.

I claim as my invention:

1. In an electronic flame detector having means constituting an input electronic stage which is controlled by flame sensing means and means constituting an output electronic stage controlling a flame relay, the improvement comprising a first source of operating voltage connected to energize the output stage and thereby cause the flame relay to be energized to check the proper operation thereof, a second source of operating voltage, means responsive to the energization of said flame relay to apply said second source of operating voltage to the input stage and thereby cause the flame relay to be de-energized, and further means responsive to said energization of the flame relay to maintain said second source of voltage.

2. In an electronic flame detector having means constituting a first electronic stage which is controlled by flame sensing means and which in turn controls means constituting a second electronic stage to render this stage nonconductive in the absence of flame, and in which the second electronic stage controls the energization of a flame relay which is energized in the presence of flame, the improvement comprising; circuit means adapted to energize said second electronic stage, further circuit means adapted to energize said first electronic stage controlled by a normally open switch of the flame relay such that the flame relay is initially energized in the absence of flame to check the proper operation thereof and said energization thereby causes said first electronic stage to be rendered operative, to cause the flame relay to be subsequently de-energized in response to the actual absence of flame, and a safe-start relay energized by said normally open switch of the flame relay, said safe-start relay having a normally open switch which shunts said flame relay switch to thereby maintain energization of said first electronic stage once said safe-start relay is initially energized.

3. A flame detector comprising; flame sensing means, a first controllable current conducting device having an input and an output, a second controllable current conducting device having an input and an output, means connecting the input of said first current conducting device to said flame sensing means to be controlled thereby, means connecting the output of said first current conducting device to the input of said second current conducting device, a flame relay having a winding and a normally open switch, means connecting said flame relay winding to the output of said second current conducting device, a first source of operating voltage connected to energize said second current conducting device and thereby cause said flame relay to be energized to check the proper operation thereof, circuit means including the normally open switch of said flame relay adapted to connect said first current conducting device to a second source of operating voltage to render said first current conducting device operative and subsequently cause said iiafrie relay to be deenergized, and further means energized by said second source of operating voltage and adapted to substantially maintain current flow through said first current conductive device as initially established 'by the normally open switch of said flame relay.

4. Conditidn sensing apparatus comprising; flame sensing means, a first and a second electron discharge device each having an input and an output circuit, means con= meeting the input circuit of said first discharge device to said flame sensing means, means connecting the output circuit of said first discharge device to the input circuit of said second electron discharge device, a flame relay having a winding and a normally open switch, circuit means connecting said flame relay winding to the output circuit of said second discharge device, a first transformer having a primary winding connected to a soiifce of alternating voltage and a secondary winding connected to supply operating voltage to said second discharge device, a second transformer having a primary winding adapted to be connected through said normally open flame relay switch to a source of alternating voltage and having a secondary winding connected to supply operating voltage to said first electron discharge device, said second discharge device thereby being rendered conductive upon initial application of voltage to the primary winding of said first transformer to cause said flame relay to be energized to check the proper operation thereof, whereupon said normally open flame switch causes said second transformer primary winding to be connected to a source of operating voltage which will in turn aflect current flow through the secondary winding of the said second transformer to cause said first electron discharge device to be energized which will then cause said flame relay to be de-energiz'ed, and further means electrically connected with said secondprimai'y winding to be energized therewith and having means to' maintain said second wind ing connected to the source of alternating voltage.

5. Condition sensing apparatus comprising; a first electron discharge device having an input circuit and an output circuit, condition sensing means, means connecting said condition sensing means to the input circuit of said first discharge device in a manner to render said first discharge device nonconductive in the presence of a given condition, a second electron discharge device having an input circuit and an output circuit, circuit means connecting the input circuit of said second discharge device to the output circuit of said first discharge device in a manner to render said second discharge device conductive only when said first discharge device is nonconductive, a relay having a winding connected to the output of said second discharge device to 'be energized thereby and having a, normally open switch, a first transformer having a primary winding adapted to be connected to a source of alternating voltage and a secondary winding connected in circuit with the output circuit of said second discharge device and said relay winding, a second transformer having a primary winding adapted to be connected through the normally open switch of said relay to a source of alternating voltage and a secondary winding connected in circuit with the output circuit of said first discharge device, and further means energized coincident with said second transformer primary winding and effective when so energized to maintain said second primary winding connected to the source of alternating voltage.

6. An electronic flame detector comprising; electrically operable flame sensing means, a first controllable current conducting device having an output circuit and having an input circuit connected to said flame sensing means such that said first current conductive device is nonconductive in the presence of flame, 'a second controllable current conducting'device having an output circuit and having an input circuit connected to the output circuit of said first current conductive device 'and arranged such that said second current conductive device is conductive upon said first current conductive device being nonconductive, a flame relay connected to the output circuit of said second current conductive device to be energized in the presence of flame, a first source of operating voltage, circuit means connecting said second current conductive device to said first source of operating voltage to thereby render said second current conductive device operative, further circuit means connecting said flame sensing means to said first source of operating voltage to render said flame sensing means operative, a second source of operating voltage, circuit means controlled by said flame relay and operative to connect said first current conductive device, to said sec ond source of operating voltage upon said flame relay being energized, and further means responsive to energization of said flame relay to maintain said first current conductive device connected to said second source of operating voltage.

7. A fuel burner control apparatus foruse with a fuel burner unit, comprising; 'a main burner control relay adapted to control the energization of the fuel burner unit; flame sensing means arranged to be subjected to the flame at the fuel burner unit, an electronic flame detector having a first and a second controllable current conducting device each having input and output electrodes, circuit means connecting said flame sensing means to the input electrodes of said first current conducting device to render said first current conducting device nonconductive in the presence of flame at the fuel burner unit, circuit means connecting the output electrodes of said first current conductive device in a controlling relation to the input electrodes of said second current conductive device to render said second current conductive device conductive in the presence of flame, a flame relay having a winding and having a normally closed and a normally open switch, circuit means connecting said flame relay winding to the output electrodes of said second current conducting device to be energized in the presence of flame; a first source of operating voltage connected to provide energizing voltage to said second current conducting device; a second source of operating voltage, circuit means controlled by said normally open flame relay switch adapted to connect said second source of operating voltage to provide operating voltage for said first current conducting device and said main burner control relay; a safe-start relay having a winding connected to be energized in response to closing of said normally open flame relay switch, a further switch controlled by said safe-start relay arranged to maintain said second current conductive device connected to said second source of operating voltage and to maintain said safe-start relay energized; and an initial energizing circuit for said main burner control relay adapted to be controlled by means responsive to the need for operation of the fuel burner unit and including said normally closed switch of said flame relay such that said main burner con trol relay may not be energized until said flame relay has been initially energized and then de-energized to check the proper operation thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,216,534 Kirk Oct. 1, 1940 

